Proximity switch assembly and method of sensing user input based on signal rate of change

ABSTRACT

A proximity switch assembly and method for detecting activation of a proximity switch assembly is provided. The assembly includes a plurality of proximity switches each having a proximity sensor providing a sense activation field and control circuitry processing the activation field of each proximity switch to sense activation. The assembly and method detects a signal associated with each proximity switch, determines a rate of change of the signal associated with the first switch and a rate of change of the signal associated with a neighboring second switch and determines whether to activate the first switch based on at least one of the first rate of signal change and second rate of signal change.

FIELD OF THE INVENTION

The present invention generally relates to switches, and moreparticularly relates to proximity switches having an enhanceddetermination of switch activation.

BACKGROUND OF THE INVENTION

Automotive vehicles are typically equipped with various user actuatableswitches, such as switches for operating devices including poweredwindows, headlights, windshield wipers, moonroofs or sunroofs, interiorlighting, radio and infotainment devices, and various other devices.Generally, these types of switches need to be actuated by a user inorder to activate or deactivate a device or perform some type of controlfunction. Proximity switches, such as capacitive switches, employ one ormore proximity sensors to generate a sense activation field and sensechanges to the activation field indicative of user actuation of theswitch, typically caused by a user's finger in close proximity orcontact with the sensor. Capacitive switches are typically configured todetect user actuation of the switch based on comparison of the senseactivation field to a threshold.

Switch assemblies often employ a plurality of capacitive switches inclose proximity to one another and generally require that a user selecta single desired capacitive switch to perform the intended operation. Insome applications, such as use in an automobile, the driver of thevehicle has limited ability to view the switches due to driverdistraction. In such applications, it is desirable to allow the user toexplore the switch assembly for a specific button while avoiding apremature determination of switch activation. Thus, it is desirable todiscriminate whether the user intends to activate a switch, or is simplyexploring for a specific switch button while focusing on a higherpriority task, such as driving, or has no intent to activate a switch.Accordingly, it is desirable to provide for a proximity switcharrangement which enhances the use of proximity switches by a person,such as a driver of a vehicle.

SUMMARY OF THE INVENTION

According to one aspect of the present invention, a method of activatinga proximity switch is provided. The method includes the step ofdetecting a first signal associated with a first proximity switch and asecond signal associated with a neighboring second proximity switch. Themethod also includes the step of determining a first rate of change ofthe first signal and a second rate of change of the second signal. Themethod further includes the step of activating the first switch based onat least one of the first rate of signal change and the second rate ofchange.

According to another aspect of the present invention, a method ofactivating a proximity switch is provided. The method includes the stepsof detecting a first signal associated with a first proximity switch anda second signal associated with a neighboring second proximity switch.The method also includes the step of determining a rate of change of thesecond signal. The method further includes the step of activating thefirst switch based on the first signal and the rate of change of thesecond signal.

According to a further aspect of the present invention, a proximityswitch assembly is provided. The proximity switch assembly includes aplurality of proximity switches each comprising a proximity sensor forproviding a sense activation field. The proximity switch assembly alsoincludes control circuitry processing the activation field of eachproximity switch, detecting a first signal associated with a firstproximity switch and a second signal associated with a neighboringsecond proximity switch, determining a first rate of change of the firstsignal and second rate of change of the second signal, and determiningwhether to activate the first switch based on at least one of the firstrate of signal change and the second rate of signal change.

These and other aspects, objects, and features of the present inventionwill be understood and appreciated by those skilled in the art uponstudying the following specification, claims, and appended drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings:

FIG. 1 is a perspective view of a passenger compartment of an automotivevehicle having an overhead console employing a proximity switchassembly, according to one embodiment;

FIG. 2 is an enlarged view of the overhead console and proximity switchassembly shown in FIG. 1;

FIG. 3 is an enlarged cross-sectional view taken through line III-III inFIG. 2 showing an array of proximity switches in relation to a user'sfinger;

FIG. 4 is a schematic diagram of a capacitive sensor employed in each ofthe capacitive switches shown in FIG. 3;

FIG. 5 is a block diagram illustrating the proximity switch assembly,according to one embodiment;

FIG. 6 is a graph illustrating the signal count for two signal channelsassociated with two neighboring capacitive sensors showing an activationmotion profile;

FIG. 7 is a flow diagram illustrating a routine for executing a methodof activating a switch of the switch assembly, according to oneembodiment; and

FIGS. 8-8B are flow diagrams illustrating the processing of the switchactivation and switch release.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

As required, detailed embodiments of the present invention are disclosedherein; however, it is to be understood that the disclosed embodimentsare merely exemplary of the invention that may be embodied in variousand alternative forms. The figures are not necessarily to a detaileddesign; some schematics may be exaggerated or minimized to show functionoverview. Therefore, specific structural and functional detailsdisclosed herein are not to be interpreted as limiting, but merely as arepresentative basis for teaching one skilled in the art to variouslyemploy the present invention.

Referring to FIGS. 1 and 2, the interior of an automotive vehicle 10 isgenerally illustrated having a passenger compartment and a switchassembly 20 employing a plurality of proximity switches 22 having switchactivation monitoring and determination, according to one embodiment.The vehicle 10 generally includes an overhead console 12 assembled tothe headliner on the underside of the roof or ceiling at the top of thevehicle passenger compartment, generally above the front passengerseating area. The switch assembly 20 has a plurality of proximityswitches 22 arranged close to one another in the overhead console 12,according to one embodiment. The various proximity switches 22 maycontrol any of a number of vehicle devices and functions, such ascontrolling movement of a sunroof or moonroof 16, controlling movementof a moonroof shade 18, controlling activation of one or more lightingdevices such as interior map/reading and dome lights 30, and variousother devices and functions. However, it should be appreciated that theproximity switches 22 may be located elsewhere on the vehicle 10, suchas in the dash panel, on other consoles such as a center console,integrated into a touch screen display 14 for a radio or infotainmentsystem such as a navigation and/or audio display, or located elsewhereonboard the vehicle 10 according to various vehicle applications.

The proximity switches 22 are shown and described herein as capacitiveswitches, according to one embodiment. Each proximity switch 22 includesat least one proximity sensor that provides a sense activation field tosense contact or close proximity (e.g., within one millimeter) of a userin relation to the one or more proximity sensors, such as a swipingmotion by a user's finger. Thus, the sense activation field of eachproximity switch 22 is a capacitive field in the exemplary embodimentand the user's finger has electrical conductivity and dielectricproperties that cause a change or disturbance in the sense activationfield as should be evident to those skilled in the art. However, itshould also be appreciated by those skilled in the art that additionalor alternative types of proximity sensors can be used, such as, but notlimited to, inductive sensors, optical sensors, temperatures sensors,resistive sensors, the like, or a combination thereof. Exemplaryproximity sensors are described in the Apr. 9, 2009, ATMEL® TouchSensors Design Guide, 10620 D-AT42-04/09, the entire reference herebybeing incorporated herein by reference.

The proximity switches 22 shown in FIGS. 1 and 2 each provide control ofa vehicle component or device or provide a designated control function.One or more of the proximity switches 22 may be dedicated to controllingmovement of a sunroof or moonroof 16 so as to cause the moonroof 16 tomove in an open or closed direction, tilt the moonroof, or stop movementof the moonroof based upon a control algorithm. One or more otherproximity switches 22 may be dedicated to controlling movement of amoonroof shade 18 between open and closed positions. Each of themoonroof 16 and shade 18 may be actuated by an electric motor inresponse to actuation of the corresponding proximity switch 22. Otherproximity switches 22 may be dedicated to controlling other devices,such as turning an interior map/reading light 30 on, turning an interiormap/reading light 30 off, turning a dome lamp on or off, unlocking atrunk, opening a rear hatch, or defeating a door light switch.Additional controls via the proximity switches 22 may include actuatingdoor power windows up and down. Various other vehicle controls may becontrolled by way of the proximity switches 22 described herein.

Referring to FIG. 3, a portion of the proximity switch assembly 20 isillustrated having an array of three serially arranged proximityswitches 22 in close relation to one another in relation to a user'sfinger 34 during use of the switch assembly 20. The middle proximityswitch 22 has neighboring proximity switches 22 on both the left andright sides. Each proximity switch 22 includes one or more proximitysensors 24 for generating a sense activation field. According to oneembodiment, each of the proximity sensors 24 may be formed by printingconductive ink onto the top surface of the polymeric overhead console12. One example of a printed ink proximity sensor 24 is shown in FIG. 4generally having a drive electrode 26 and a receive electrode 28 eachhaving interdigitated fingers for generating a capacitive field 32. Itshould be appreciated that each of the proximity sensors 24 may beotherwise formed such as by assembling a preformed conductive circuittrace onto a substrate according to other embodiments. The driveelectrode 26 receives square wave drive pulses applied at voltage V_(I).The receive electrode 28 has an output for generating an output voltageV_(O). It should be appreciated that the electrodes 26 and 28 may bearranged in various other configurations for generating the capacitivefield as the activation field 32.

In the embodiment shown and described herein, the drive electrode 26 ofeach proximity sensor 24 is applied with voltage input V_(I) as squarewave pulses having a charge pulse cycle sufficient to charge the receiveelectrode 28 to a desired voltage. The receive electrode 28 therebyserve as a measurement electrode. In the embodiment shown, adjacentsense activation fields 32 generated by adjacent or neighboringproximity switches 22 overlap slightly, however, overlap may not existaccording to other embodiments. When a user or operator, such as theuser's finger 34, enters an activation field 32, the proximity switchassembly 20 detects the disturbance caused by the finger 34 to theactivation field 32 and determines whether the disturbance is sufficientto activate the corresponding proximity switch 22. The disturbance ofthe activation field 32 is detected by processing the charge pulsesignal associated with the corresponding signal channel. When the user'sfinger 34 contacts two activation fields 32, the proximity switchassembly 20 detects the disturbance of both contacted activation fields32 via separate signal channels. Each proximity switch 22 has its owndedicated signal channel generating charge pulse counts which isprocessed as discussed herein.

Referring to FIG. 5, the proximity switch assembly 20 is illustratedaccording to one embodiment. A plurality of proximity sensors 24 areshown providing inputs to a controller 40, such as a microcontroller.The controller 40 may include control circuitry, such as amicroprocessor 42 and memory 48. The control circuitry may include sensecontrol circuitry processing the activation field of each sensor 22 tosense user activation of the corresponding switch by comparing theactivation field signal to one or more thresholds pursuant to one ormore control routines. It should be appreciated that other analog and/ordigital control circuitry may be employed to process each activationfield, determine user activation, and initiate an action. The controller40 may employ a QMatrix acquisition method available by ATMEL®,according to one embodiment. The ATMEL acquisition method employs aWINDOWS® host C/C++ compiler and debugger WinAVR to simplify developmentand testing the utility Hawkeye that allows monitoring in real-time theinternal state of critical variables in the software as well ascollecting logs of data for post-processing.

The controller 40 provides an output signal to one or more devices thatare configured to perform dedicated actions responsive to detectedactivation of a proximity switch. For example, the one or more devicesmay include a moonroof 16 having a motor to move the moonroof panelbetween open and closed and tilt positions, a moonroof shade 18 thatmoves between open and closed positions, and lighting devices 30 thatmay be turned on and off. Other devices may be controlled such as aradio for performing on and off functions, volume control, scanning, andother types of devices for performing other dedicated functions. One ofthe proximity switches 22 may be dedicated to actuating the moonroofclosed, another proximity switch 22 may be dedicated to actuating themoonroof open, and a further switch 22 may be dedicated to actuating themoonroof to a tilt position, all of which would cause a motor to movethe moonroof to a desired position. The moonroof shade 18 may be openedin response to one proximity switch 22 and may be closed responsive toanother proximity switch 22.

The controller 40 is further shown having an analog to digital (A/D)comparator 44 coupled to the microprocessor 42. The A/D comparator 44receives the voltage output V_(O) from each of the proximity switches22, converts the analog signal to a digital signal, and provides thedigital signal to the microprocessor 42. Additionally, controller 40includes a pulse counter 46 coupled to the microprocessor 42. The pulsecounter 46 counts the charge signal pulses that are applied to eachdrive electrode of each proximity sensor, performs a count of the pulsesneeded to charge the capacitor until the voltage output V_(O) reaches apredetermined voltage, and provides the count to the microprocessor 42.The pulse count is indicative of the change in capacitance of thecorresponding capacitive sensor. The controller 40 is further showncommunicating with a pulse width modulated drive buffer 15. Thecontroller 40 provides a pulse width modulated signal to the pulse widthmodulated drive buffer 15 to generate a square wave pulse train V_(I)which is applied to each drive electrode of each proximity sensor/switch22. The controller 40 processes one or more control routines, shownincluding control routines 100 and 200 stored in memory to monitor andmake a determination as to activation of one of the proximity switches.

The control routines 100 and 200 process the plurality of proximityswitches 22 and perform a method of sensing user input on the switchesand activating the appropriate proximity switch associated with theproximity switch assembly 20. The method includes the steps ofgenerating an activation field with each of a plurality of proximitysensors associated with a plurality of proximity switches, and detectinga signal associated with each of a plurality of proximity sensorsassociated with the proximity switches due to presence of a user. Themethod also detects a peak amplitude of a first signal associated with afirst proximity switch and determines a rate of change of the firstsignal following the peak amplitude detection and a rate of change of asecond signal associated with a neighboring second proximity switch. Themethod further determines whether to activate the first switch based onat least one of the rate of change of the first signal and rate ofchange of the second signal. The method further enters an explorationmode when the rate of change of the first signal and rate of change ofthe second signal are greater than a threshold. The method determinesactivation of the current signal channel when at least one of the rateof change of the first signal and the rate of change of the secondsignal is less than a threshold value. The method further sums theabsolute value of rate of change of the first signal and absolute valueof rate of change of the second signal, compares the summed value to asum threshold value, and activates the current channel switch when thesummed value is less than the sum threshold value. The rate of change ofboth the first signal and the second signal are determined during a timeperiod following detection of the peak signal. The largest amplitudesignal associated with the plurality of activation fields is processedto determine activation of one of the proximity sensors.

Referring to FIG. 6, the change in sensor charge pulse counts shown as ΔSensor Count for two signal channels associated with two neighboring(i.e., adjacent) proximity switches 22 shown in FIG. 3, is illustratedaccording to one example. The change in sensor charge pulse count is thedifference between an initialized referenced count value without anyfinger or other object present in the activation field and thecorresponding sensor reading. In this example, the user's finger entersthe activation fields 32 associated with each of two neighboringproximity switches 22, generally one sense activation field at a timewith overlap between adjacent activation fields 32 as the user's fingermoves across the array of switches. Signal channel 1 shown by solid line50A is the change (Δ) in sensor charge pulse count associated with afirst capacitive sensor 24, and signal channel 2 shown by dashed line50B is the change in sensor charge pulse count associated with theadjacent or neighboring second capacitive sensor 24. In the disclosedembodiment, the proximity sensors 24 are capacitive sensors. When auser's finger is in contact with or close proximity of a sensor 24, thefinger alters the capacitance measured at the corresponding sensor 24.The capacitance is in parallel to the untouched sensor pad parasiticcapacitance, and as such, measures as an offset. The user or operatorinduced capacitance is proportional to the user's finger or other bodypart dielectric constant, the surface exposed to the capacitive pad, andis inversely proportional to the distance of the user's limb to theswitch button. According to one embodiment, each sensor is excited witha train of voltage pulses via pulse width modulation (PWM) electronicsuntil the sensor is charged up to a set voltage potential. Such anacquisition method charges the receive electrode 28 to a known voltagepotential. The cycle is repeated until the voltage across themeasurement capacitor reaches a predetermined voltage. Placing a user'sfinger on the touch surface of the switch 24 introduces externalcapacitance that increases the amount of charge transferred each cycle,thereby reducing the total number of cycles required for the measurementcapacitance to reach the predetermined voltage. The user's finger causesthe change in sensor charge pulse count to increase since this value isbased on the initialized reference count minus the sensor reading.

The proximity switch assembly 20 is able to recognize the user's handmotion when the hand, particularly a finger, is in close proximity tothe proximity switches 22, to discriminate whether the intent of theuser is to activate a switch 22, explore for a specific switch buttonwhile focusing on higher priority tasks, such as driving, or is theresult of a task such as adjusting the rearview mirror that has nothingto do with actuation of a proximity switch 22. The proximity switchassembly 20 may operate in an exploration or hunting mode which enablesthe user to explore the touch sensor keypads or buttons of the switchassembly 20 by passing or sliding a finger in close proximity to theswitches without triggering an activation of a switch until the user'sintent is determined. The proximity switch assembly 20 monitorsamplitude of a signal generated in response to the activation field foreach switch, detects a peak signal associated with one of the switches,determines a rate of change of a first signal associated with a firstswitch following the peak detection, and a rate of change of a secondsignal associated with a neighboring second switch, and determineswhether to activate the first switch based on at one of the rate ofsignal change of the first signal and rate of change of the secondsignal. The proximity switch assembly 20 further enters an explorationmode when the rate of change of the first signal and the rate of changeof the second signal are greater than a threshold. As a result,exploration of the proximity switch assembly 20 is allowed, such thatusers are free to explore the switch interface pad with their fingerswithout inadvertently triggering an event, the interface response timeis fast, activation happens based on rate of change in the signal(s),and inadvertent activation of the switch is prevented or reduced.

As shown in FIG. 3, as the user's finger 34 approaches a proximityswitch 22 associated with signal channel 1, the finger 34 enters theactivation field 32 associated with the sensor 24 which causesdisruption to the capacitance, thereby resulting in a Δ sensor countincrease as shown by signal 50A in the activation motion profile of FIG.6. The proximity switch assembly monitors the current signal channel 50Aof the first switch as well as signal channels of neighboring switches,such as second signal channel 50B, and determines whether the operatorintends to press a button for activation of the current switch orexplore the interface based on one or both of the rate of change of thefirst signal and a neighboring switch signal channel. The system andmethod monitors the first signal 50A to determine when the first signal50A exceeds a level threshold (LVL_THRESHOLD) count indicative of anactive signal channel having a Δ sensor count value indicative ofactivity on a sensor greater than noise. The first signal channel 50Acrosses the LVL_ACTIVE threshold at point 52 and rises up to a peaksignal at point 54.

The first signal 50A is shown decreasing thereafter. Upon detection ofthe peak signal PEAK_CH1 at point 54, the system and method determines arate of change of the first signal channel following the peak detectionand a rate of change of a second signal channel associated with aneighboring switch following peak detection. The rate of change of thefirst signal channel 50A is determined during a time period Δ timeduring which the signal 50A drops from the peak channel at point 54 to asignal level at point 56. According to one embodiment, the Δ time is apredetermined time less than 500 milliseconds, and more particularly ofabout 100 milliseconds, according to one example. During the 100millisecond time delay, the first signal 50A drops by a value shown asDELTA CH1. The signal channel for each and every neighboring channel,such as second signal 50B is also monitored. One neighboring secondsignal channel 50B is shown by dotted lines rising up to a peak valueand dropping. The second signal channel associated with the neighboringswitch has a rate of change of signal during the delay time Δ time shownrising up from point 58 to point 60 shown as rate of change DELTA CH2.Thus, the system and method determines both a rate of change of thefirst signal channel 50A shown by delta channel CH1 and a rate of changeof the neighboring second signal channel 50B shown as DELTA CH2 duringtime period Δ time, and uses the rate of change signal DELTA CH1 andDELTA CH2 to determine whether to activate the first switch associatedwith the first signal channel 50A. The system and method may make adecision as to whether to activate the first switch based on either ofthe rate of change of the first signal channel and the rate of change ofthe neighboring second signal channel or on a combination of both of therate of change signals DELTA CH1 and DELTA CH2. In one embodiment, thesystem and method monitors each of the rate of change signals DELTA CH1and DELTA CH2 and further sums up the absolute values of the signalsDELTA CH1 and DELTA CH2 and compares the summed total to a sum thresholdtest value which may be based on a proportion or multiplication factorof the peak signal PEAK CH1 at point 54 of the current first signalchannel. The multiplication factor may be 0.5 (or 50%), for example.

A routine 100 for executing a method of activating a proximity switch ofthe proximity switch assembly is illustrated in FIG. 7, according to oneembodiment. Method 100 begins at step 102 and proceeds to process thesignal channel associated with each proximity switch of the switchassembly in each of blocks 200, which may occur with parallelprocessing. Next, method 100 proceeds to step 104 to monitoring thesignal amplitude of each of the signal channels 1-n to find the maximumsignal channel associated with one of the switches. At step 106, method100 monitors the signal for all signal channels identified as ich 1 to nand stores the index values in memory. Next, at decision block 108,method 100 determines if there is a switch activated. If a switch isactivated, method 100 ends at step 126. If none of the switches areactivated, method 100 proceeds to decision step 110 to determine if thecurrent switch (ich) is set to activate_switch and, if not, returns tostep 106. If the current switch (ich) is set to activate_switch, method100 proceeds to decision step 112 to determine if the maximum ichannelis equal to the index of channel ich and, if not, proceeds to step 114to set the activate switch (ich) equal to zero and to set the switchstatus (ich) equal to the SW_NONE which is the state in which there isno sensor activity detected, before returning to step 106. If themaximum ichannel is set equal to the index of channel ich, method 100proceeds to step 116 to check all neighboring switch buttons that arenot in the SW_NONE state. Accordingly, any switches or buttons that havesome sensor activity and all neighboring switches to the current switchhaving the current maximum signal channel are monitored. Proceeding toblock 118, method 100 monitors the rate of change of the current signalchannel associated with the current switch and each neighboring signalchannel associated with each neighboring switch during a predeterminedtime period following the peak amplitude of the current channel.Included in block 118 is a calculation of test_level set equal toK×peak_channel (ich), where K is a multiplication factor such as 05, andcalculation of channel_sliding set equal to Kcs×peak_channel (ich),where Kcs is a multiplication factor such as 0.1. Additionally, a valueDELTA is determined which is a sum of the absolute values of DELTA ichand DELTA inb, where DELTA ich is the peak channel rate of change duringthe time delay, and DELTA inb is the rate of change of the signalchannel of the neighboring channel when the peak of the current signalchannel is detected minus the signal channel of the neighboring channelat the end of the time period Δ time. Method 100 then proceeds todecision step 120 to make the following decisions: determine if DELTA isgreater than a test level; and determine if DELTA_ich is greater thanchannel_sliding; and determine if DELTA_inb is greater thanchannel_sliding. If any of the three conditions in decision block 120are no, routine 100 returns to step 116. If all of the conditions setforth in decision block 120 are yes, routine 100 proceeds to decisionblock 122 to determine if the channel peak is consistent with theprevious peaks and, if so, sets the current switch ich to active stateat step 124 before ending at step 126. Otherwise, method 100 returns tostep 116. Accordingly, method 100 determines whether or not to activatethe current signal channel based on at least one of the rate of signalchange of the current switch channel and rate of change of theneighboring switch channel(s).

Referring to FIGS. 8-8B, the processing of the individual signalchannels associated with the plurality of switches is illustrated,according to one embodiment. Routine 200 begins at step 202 to processthe current channel ich and proceeds to decision step 204 to determineif the switch status (ich) is set equal to the SW_NONE state and, if so,proceeds to step 206 to set the channel peak (ich) equal to zero andsets the activate_switch (ich) equal to zero. Routine 200 then proceedsto decision step 208 to determine if the current channel (ich) isgreater than LVL_ACTIVE) and, if so, sets the channel peak (ich) equalto the current channel (ich); and further sets the switch status (ich)equal to the switch_active. The switch_active state is the state inwhich activity as determined by the sensor is high enough to warrantactivation, hunting/exploration, or casual motion of the switchassembly.

Returning to decision step 204, if the current switch status (ich) isnot equal to the SW_NONE state, then routine 200 proceeds to decisionstep 214 to determine if the switch status (ich) is equal to theswitch_active state which is the state in which some activity isdetected by the sensor, but not though to trigger activation of theswitch at that point in time. If the switch is in the switch_activestate, routine 200 proceeds to step 224 shown in FIG. 8A to set thechannel peak (ich) equal to the maximum value. Next, at decision step226, routine 200 determines if the current channel (ich) is less thanLVL_ACTIVE and, if so, proceeds to step 228 to set the switch statusequal to the SW_NONE state, before ending at step 210. If the channel isnot less than LVL_ACTIVE, routine 200 proceeds to decision step 230 todetermine if the channel is less than the channel peak and, if not, endsat step 210. If the channel is less than the channel peak, routine 200proceeds to step 232 to set the Δ time equal to Δ time and to furtherset the switch status equal to the switch_triggered state. Theswitch_triggered state is the state in which the switch button isconsidered for activation after a time Δ. Next, at step 234, routine 200looks for all inb switch neighbors of current switch ich, and thenproceeds to step 236 to set the neighboring channel (inb) to the channelat ich peak (inb), before ending at step 210.

Returning to FIG. 8, if the switch status is not equal to theswitch_active state in decision step 214, routine 200 proceeds todecision step 216 to determine if the switch status is equal to theswitch_triggered state and, if so, proceeds to decision step 238 in FIG.8B. In decision step 238, routine 200 determines if the Δ time isgreater than zero and, if not, proceeds to step 240 to setActivate_Switch equal to one; to set Switch_Status equal toSwitch_Releasing; and to set the Switch_Release_Timer equal toWaitforrelease, before ending at step 210. If the Δ time is greater thanzero, routine 200 proceeds to decision step 242 to determine if thecurrent channel ich is greater than the channel peak (ich) and, if so,sets the channel peak (ich) equal to current channel and sets the switchstatus equal to switch_active at step 248, before ending at step 210. Ifthe signal is not greater than the signal peak, routine 200 proceeds todecision step 244 to determine if the channel is less than LVL_ACTIVEand, if so, sets the switch status equal to SW_NONE state at step 246,before ending at step 210. If the channel is not less than LVL_ACTIVE,routine 200 ends at step 210.

Returning to decision step 216 in FIG. 8, if the switch status is notequal to the switch_triggered state, routine 200 proceeds to decisionstep 218 to determine if the channel is less than the LVL_ACTIVE and, ifnot, ends at step 210. If the channel is less than LVL_ACTIVE, routine200 proceeds to decision step 220 to determine if the switch activatedis equal to ich and, if not, ends at step 210. If the switch activatedis set equal to ich, routine 200 proceeds to step 222 to reset allchannels ii=1-n; to set the Activate_Switch equal to zero; to setChannel_Peak equal to zero; to set Switch_Status equal to zero; to setSwitch_Release_Timer equal to zero, and to set Switch_Activated equal tono switch before ending at step 210. It should be appreciated thatroutine 200 may be repeated for each of the signal channels 1 through nand employed in routine 100.

Accordingly, the determination routine advantageously determinesactivation of the proximity switches based on a first signal and a rateof change of the first signal associated with a first proximity switchand rate of change of a second signal associated with a neighboringsecond switch. It should be appreciated that all neighboring switchesmay be monitored to determine activation of a switch. The routineadvantageously allows for a user to explore the proximity switch padswhich can be particularly useful in an automotive application wheredriver distraction can be avoided.

It is to be understood that variations and modifications can be made onthe aforementioned structure without departing from the concepts of thepresent invention, and further it is to be understood that such conceptsare intended to be covered by the following claims unless these claimsby their language expressly state otherwise.

We claim:
 1. A method of operating a proximity switch comprising:detecting a first signal associated with a first proximity switch forperforming a first function and a second signal associated with aseparate neighboring second proximity switch for performing a secondfunction; determining with a controller a first rate of change of thefirst signal and a second rate of change of the second signal; andperforming the first function of the first switch based on both thefirst rate of change and the second rate of change.
 2. The method ofclaim 1 further comprising the step of detecting a peak amplitude of thefirst signal, wherein the first rate of change of the first signal andthe second rate of change of the second signal is determined followingthe peak amplitude detection.
 3. The method of claim 1 furthercomprising the step of entering an exploration mode when the first rateof change of the first signal and the second rate of change of thesecond signal are greater than a threshold.
 4. The method of claim 1,wherein the method determines activation of the first signal when atleast one of the first rate of change of the first signal and secondrate of change of the second signal is less than a threshold value. 5.The method of claim 1 further comprising the step of summing an absolutevalue of the first rate of change of the first signal and an absolutevalue of the second rate of change of the second signal, comparing thesummed value to a sum threshold value, and performing the first functionof the first switch when the summed value is less than the sum thresholdvalue.
 6. The method of claim 1, wherein the first rate of change of thefirst signal is determined during a predetermined time period followingdetection of the peak amplitude, and the determination of second rate ofchange of the second signal is determined during the predetermined timeperiod.
 7. The method of claim 6, wherein the predetermined time periodis less than 500 milliseconds.
 8. The method of claim 1, wherein aplurality of activation fields are generated for a plurality ofproximity sensors associated with a plurality of proximity switches, andwherein the largest amplitude signal associated with the plurality ofactivation fields is processed to determine performing a function of oneof the proximity switches.
 9. The method of claim 1, where the proximityswitch is installed on a vehicle for use by a passenger in the vehicle.10. The method of claim 1, wherein the proximity switch comprises acapacitive switch comprising one or more capacitive sensors.
 11. Aproximity switch assembly comprising: a plurality of proximity switcheseach comprising a proximity sensor for providing a sense activationfield; and control circuitry processing the activation field of eachproximity switch, detecting a first signal associated with a firstproximity switch for performing a first function and a second signalassociated with a separate neighboring second proximity switch forperforming a second function, determining a first rate of change of thefirst signal and second rate of change of the second signal, andperforming the first function of the first switch based on both thefirst rate of signal change and the second rate of change.
 12. Theproximity switch assembly of claim 11, wherein the control circuitryfurther detects a peak amplitude of the first signal and determines thefirst rate of change of the first signal and the second rate of changeof the second signal following the peak amplitude detection.
 13. Theproximity switch assembly of claim 12, wherein the determination of thefirst rate of change of the first signal and the second rate of changeof the second signal occurs within a predetermined time period of lessthan 500 milliseconds.
 14. The proximity switch assembly of claim 11,wherein the control circuitry enters an exploration mode when the firstrate of change of the first signal and the second rate of change of thesecond signal are greater than a threshold.
 15. The proximity switchassembly of claim 11, wherein the control circuitry sums an absolutevalue of the first rate of change of the first signal and an absolutevalue of the second rate of change of the second signal, compares thesummed value to a sum threshold value, and performs the first functionof the first switch when the summed value is less than the sum thresholdvalue.
 16. The proximity switch assembly of claim 11, wherein theproximity switch is installed on a vehicle for use by a passenger in thevehicle.
 17. The proximity switch assembly of claim 11, wherein theproximity switch comprises a capacitive switch comprising one or morecapacitive sensors.